Machine tool, and especially radial drilling machine



July 21, 194-2. EG RD 2,290,766

MACHINE-TOOL AND ESPECIALLY RADIAL DRILLING MACHINE Filed Jan. 4, 1940 5 Sheets-Sheet 1 July 21, 1942. M, PEGARD. I 2,290,766

MACHINE-TOOL AND ESPECIALLY RADIAL DRILLING MACHINE Filed Jan. 4, 1940 5 Sheets-Sheet 2 Jul 21, 1942.

V M. PEGARD 2,290,766

MACHINE-TOOL AND ESPECIALLY RADIAL DRILLING MACHINE Filed Jan. 4, 1940 5 Sheets-Sheet 3 M. PEGARD July 21, 1942.

MACHINE-TOOL A ND ESPECIALLY RADIAL DRILLING; MACHINE 5 Sheets-Sheet 4 Filed Jan. 4,1940

July 21, 1942. M. PEGARD 2,290,766

MACHINE-TOOL AND ESPECIALLY RADIAL DRILLING MACHINE Filed-Jan. 4, 1940 5 Sheets-Sheet 5 JIM/"6%? Mcefl W) j] kid WIT/6;.-

Patented July 21,

momma 'roonnnn ESPECIALLY RADIAL DRILLING mcnmn Marcel Pgard, Paris, France Application January 4, 1940, Serial No. 312,311

In France September 2, 1939 1-: Claims. (cow-21) The present invention relates to machine'- tools, such for instance as a radial drilling machine, including a drill carrying carriage adapted about a cylindrical column.

The object of'the present invention is to provide improvements in machines of this kind, and,

in particular to provide devices, adapted to be used in connection with such machines, for producing, .by the mere operation of push-buttons or the like, the locking and unlocking of the arm of the drilling machine with respect. to the column and of the carriage with respect to said radial arm, these devices simultaneously ensuring the locking and unlocking of these various eleto move along a radial arm, pivotally mounted away, of a radial drilling machine made according to the invention;

Fig. 2 is a sectional view ill a horizontal plane,

on the line lI-H of Fig, 1;

Fig. 3 is a vertical section on the line III-III of Fig. 1; i

Fig. 4 is a vertical section on the line IV--IV I of Fig. 1;

merits without the tool being displaced from its slideway of the carriage along the arm, the connection between said shaft and the arm of the drilling machine being designed in such manner as to be able to absorb, without transmitting them, the reactions that result from the lockin and unlocking operations, in said shaft, whereby said reactions act practically neither on the arm nor on the carriage and consequently do not produce any displacement of the tool from its correct working position.

Fig. 5 is a sectional view,on an enlarged scale, on the line V-V of Fig. 2;

Fig. 6 is a sectional view on the of Fig. .5;

Fig. 7 is a diagram of the electric connections of a locking device working in two'steps, according to the invention;

Fig. 8 is a diagram of the electric connections of a locking device including automatic signalling means;

Fig. 9 is an elevational view of l and 2. l

The radial drilling machine shown by the drawings includes the following essential eleline ments: A fixed cylindrical column I supports a radial arm 2 pivotally mounted thereon and bearing on said column throughiits tubular sleeve 3. A carriage I, movable along the slideways or tracks 2a, 2b of the radial arm, carries the drill- The driving of this shaft is advantageously ensured by an electric motor.

According to an interesting feature of the present invention, the immobilization of the arm on the column is prepared by producing a radial locking, which will be hereinafter called temporary locking, obtained by means of parts which are brought into play slightly before, and during, the final locking operation, whereby the arm is wholly immobilized during the arm locking and releasing operations. The temporary locking action may .be supplied by an electromagnetic device connected in shunt with the final locking control motor, which ensures the quick and automatic succession of the two locking operations.

Other features of the present invention will ing tool 5 and its driving motor, which is not visi'ble on the drawings. The sleeve 3 of arm 2 is cut away transversely so as to constitute two arcuate bands, with lugs 3a and 3b at their ends, having a certain elasticity and. the tight application of which against the cylindrical surface of the column produces the locking of the arm in any desired angular position.

These lugs 3a and 3b are interconnected, by meansPof individual connecting rods 6a, 6b,'each with a crank pin Ia, lb, respectively, said crank pins being mounted in opposition on a driving shaft 8 parallel to slidewaysla, 2b. Thesecrank pins act, through the intermediate of needle bearings (or ball hearings) on annular parts to each other and to apply the inner surfaces appear from the following detailed description of some specific embodiments thereof. Preferred embodiments of the present invention will be hereinafter described with reference to the accompanying drawings, given merely by way of example,.and in which:

Fig. l is a side elevational view, with parts out it isdesiredto avoid any displacement of the tool from its correct working position, the locking and-unlocking of the radial arm, with respect to the column must not produce any effort capable of producing a pivoting displacement-even through a very small angle, of the arm about the a detail of Figs.

axis of the column. As arm 2 is mounted on ball bearings and therefore turns very freely about the column, the above mentioned condition involves neutralizing,during the locking operation, any force which would act on the arm c and d being the respective distances of the linesof action of forces Ra and Rb from axis 0. Neglecting the very small difference between these distances c and'd, the reactions Raand Rb, which are very variable during the locking, should at least remain constantly equal to each .other in absolute value and opposed in direction.

As this condition is not exactly complied with in the industrial construction of machine tools, there always remains a tangential resultant force in eccentrics Ia, lb, which force is transmitted crank arm 32 in bearing Ill. The locking control shaft 3 extends with a certain play (which is rather considerable) through hollow journal 35 and an intermediate ring 33, itself housed with a certain play in an annular recess 39 provided in the central part of crank arm 32.

The connection between shaft 3 and crank arm 32 is obtained through a double system of keys, In a first diametral plane, keys 4| and 42 are housed with a certain radial play in corresponding grooves of the crank arm 32 and of the intermediate ring 33. In a second diametral plane, keys 43 and 43, extending perpendlcu' larly to the first mentioned set of keys, are

to the arni through the intermediate of bearing Ill in machine tools of the type known up to this time.

On the other hand, if lug 3a, for instance, comes into contact with the column before the inner edge of lug 31) has come into contact with said column, there is produced, at a point such as A,aj reaction of the column which is added to the above considered system of forces. Portion 3a ceases to move, but the whole of the crank pins la and lb must move the more as the portion 3b of the sleeve is farther from the column, and this will produce a movement of, rotation of the arm around the column.

According to the invention, I avoid any detrimental displacement of the arm with respect to the column owing to the following arrangements, taken in combination:

Radial arm' final locking device This device includes a control motor I! (Figs.

1, 3 and'4) flxed through its base on a bracket it, carried by the rear part of the arm 2 of the drilling'machine. This hollow bracket ll constitutes a casing containing a speed reducing gear, with a tangential screw l5, mounted on the shaft l6 of the motor and meshing with helical wheel H, which is keyed on an intennediate shaft 4 l3. This shaft l8 carries, at its other end, a

the locking of arm 2. This mounting is visible on Fig. 5. Crank arm32 is fixed by means of screws 33 on a ring 35 acting as journal and oscillating in a brass bearing 36 immobilized by means of studs 31 in a support ll rigid with the arm of the drilling machine. The distance from crank pin 3| to the axis of shaft I3 is smaller than the radius of crank arm 32. Therefore, a.

continuous rotation of said intermediate shaft in the direction of arrow 53 produces oscillations of.

housed, with thesame radial play, in grooves provided both in ring 38 and in shaft 8, longitudinally.

Owing to this arrangement, crank arm 32 can transmit its rotary motion to ring 33, while leaving it free to move to a certain extent in the diametral plane containing keys H and 42. Then, ring 33 in turn transmits the rotary movement to control shaft 3, while allowing the latter to assume slight transverse displacements in the plane of keys 33-, with respect to ring 33.

At the end of shaft 3, immediately close to crank arm 32, are mounted the two eccentrics Ia and lb which control the connecting rods 6a and 31: serving to lock arm 2 on the column (Fig. 2).

This shaft 3 is guided, or joumalled, at the other end of the arm of the drilling machine, in a bearing H, which may, in some cases, be of the swivel type. l

The deformable coupling system which has just been described therefore permits the locking a and the elastic reaction of shaft a mounted at the other end of the arm in bearing ll rigid with said arm.

It is clear that these resistance forces are very small, since the keys are suitably lubricated and the displacement of shaft 3 is very small in comparison to the considerable free length of this shaft. However, in cases when this is necessary, the action of these forces is nullified bymeans of an auxiliary device, called temporary locking device" in the following description.

Temporary locking device The left hand side of Fig. 1 shows, in axial section, thesleeve 3'rigid with arm 2 which ,is mounted on the column. Fig. 2 gives a transverse section of the system and Fig. 9 an elevational view thereof.

Sleeve 3 is provided, on the side opposed to the arm of the drilling machine, with a -kind of tongue or projection 5|, substantially rectangular, and the longer sides ila, iib of which are in axial planes. This tongue 5| is thus given a certain longitudinal flexibility, but it is rigid in any direction transverse with respect to the column. This part it is provided, on the inner face thereof, with three bosses or projections 52, I3, 34 the inner surfaces of which are made exactly of the radius of the column and are adapted to act as looking shoes. These bosses constitute the cores .of three electromagnets the windings II, II, and ll of which are energized, for instance, by three-phase current.

When current flows through the windings II,

It, and It in question, the magnetic circuit of the corresponding electro-magnet cores is closed through the metal of the column and the shoes II,- II and 54 are tightly applied against the column. Most of the lines of force of the magnetic ileld which cause (the shoes to adhere against the column are perpendicular to the air gap and are directed toward the axis of the column. If 1" is the resultant of the forces of application produced in the three shoes, and 6 the coemcient of friction of said shoes against the column when the electro-magnets are energized, the force opposing the rotation of the arm of the drilling machine is equal to axF. In order to obtain the desired result, the force P which produces the temporary locking of the arm on the column must act during the locking and unlocking operations and its intensity, multiplied by the coeflicient of friction 8, must be greater than the resultant of the forces above mentioned, that isv to saythe elastic reaction of the locking control shaft I on the arm and the frictional resistance of the radially movable keys II, I, 43, 4|.

Electric control of the two locking devices Figs. '2 and 8 show the diagrams of the con- Jnagnet it which serves to operate said contactor.

A control button .8, preferably a push-button,

permits of closing the circuit of electro-magnet I, which closes the circuit of motor II by means of armature 5. At the same time, blade '1 closes the contact which maintains the energizing of the electro-magnet it.

Cam II, which is keyed on intermediate shaft It, includes two circular arc portions Ila, III), of different radii, joined by inclined parts I and Y which, during the rotation of the cam, displace in opposite directions the sliding rod 56 of switch II, through the medimn of contact roller 55, A spring II is adapted constantly to urge roller 55 against the edge of cam II. Rod is provided with two transverse bars Ila and Ilb which alternately establish'a contact between conductors under tension, produce the temporary locking of sleeve I, the locking shoes being applied against column I. contactor I remains in the closing position, owing to the fact that blade" is attracted. When cam 20, driven by motor II, has turned through about 180'. in the direction of arrow 5., crank arm II has come into the position of-Fig. 8, which corresponds to the locking of "the arm by the eccentrics la, lb acting on lugs Ia, lb (Fig. 2). From this time on, roller SI starts running on the inclined portion Y of the cam I0. Rod Ilb leaves the corresponding contacts, whereas rod Ila has not yet come on its respective contacts. Circuit llll being opened,

and button 68 being released, contactor it comes back to its inoperativeposition, thus opening the circuit of the motor. But motor II keeps running, by inertia, a time sufllcient for causing roller ii to run through the whole length of inclined surface Y, so that said roller comes into contact with the section Ila of the cam, which enables transverse rod Ila to close the contact between conductors to and II. Then the motor stops, crank arm .32 remaining in the locking position. v

The unlocking or release of arm I is obtained by a new pressure exerted on control button 6|, which causes contactor 65 to work "and motor II to resume its movement in the same direction. Shaft I8 and cam II are given a further -,rotation through an angle of 180 in the direction of arrow 50, which brings back connecting rod II and crank arm 3I into the released" position of the lugs to and 3b of the sleeve. As in the preceding case, shoes SI, 53, and SI produce, by magnetic attraction on column I, a temporary locking of the arm. whereby the mechanical releasing operation' can take place without modify-v ing the correct positioning of the tool. i

The unlocking or release takes place automatically when roller 55 moves past inclined portion X, of the cam, when bar Ila opens circuit "-1., which produces the opening of contactor 5. However, the inertia of motor II is determined insuch manner that roller 55 hardly moves past the end of inclined portion x and permits the small bar IIb to re-establish the contact between l9 and 10..

l and 10, according as roller touches arc Ila or are Ilb.

windings II, I3, 54', corresponding to the electro-magnets associated with the shoes II, II,

arm II then occupying the position shown by Fig.7, in which crank pins la and lb and the lugs la and 3b of the sleeve-are in the disengaged" state. Electra-magnet is then energized, be-

tween the .phases I and II" of the current, and contactor i5 is operated so as to'close the depresses button It, connecting rod II and crank Therefore a depressing of push-button I has for its effect to produce, successively, the temporary locking of the sleeve on the column and the final locking of the arm of the drilling machine,. alternately with the releasing operations. 2

If it is desired to increase the period of time elapsing between the two operations, to wit the temporary locking or releasing and the final locking or releasing, respectively,'-it suflices to interpose a time delay relay between contactor 65 and motor II. This relay chiefly includes windings II, II, II which, once the contactor 65 has been brought into closing positional:- tract blades 15, it, 11, respectively, the movement of which is suitably braked, until the latter close their respective contacts.

It is possible simultaneously to obtain the locking of the arm on the column and-that; of carriage 4 on the arm of the drilling machine. For

. this purpose, the oscillating control shaft '8 can be ribbed'a nd it transmits its oscillations to an eccentric crank pin which shares the sliding dis placements of can'iage 4 along the arm. This eccentric crank pin will act on a device such as circuit of the motor. Motor II starts running agg'gelectro-magnets II, II and it, placed that described in the French Patent No. 845,093

of April 22, 1938, which ensures the locking of responds to the locking operations.

ing reactions capable of causing the arm to pivot about the column.

The arrangement of Fig. 8 includes, in addition to the means illustrated by Fig. 7, push-buttons separately adapted to produce the locking and the releasing of the arm, and signal lamps which are switched on as soon as one or the other of these two operations has been completed.

The elements which exist already in the arrangement of Fig. 7 are designated by the same reference numerals in Fig. 8.

This device works, for the purposes just above set forth, in the following manner:

Cam 20 and switch 2| occupying the respective positions shown by Fig. 7, the operator depresses, for instance, push button 88, which cor- The circuit of the energizing electro-magnet B6 of the contactor of the motor 85-86 is closed through the following elements: conductor I08, winding 86, conductor contact 80, conductors |02||I3, bar 2|b of switch 2|, and return conductors Ii-I05 leading back to the feed system. Contactor 8588 is brought into; the closing position and motor It starts. running.

The working of contactor 85-88, which is provided with a double armature, produces the simultaneous application of the plates 81 and 88 onto their respective contactstuds I01 and I08. These blades are connected in shunt with each of the push-buttons 80, 8|, and they maintain the energizing of the electro-magnet 86 when said above mentioned push-buttons cease to be depressed.

When cam 20, having turned through 180 in the direction of arrow 50, has nearly come into the position of Fig. 8, which corresponds to the locking of the arm on the column, as above, the bar 2|b of the switch 2| leaves its contacts.

Same as push-buttons 8| and 8|), blades 81 and 88 are each connected in series with the contact studs corresponding to the bars 2|a and MD of the switch 2|. Consequently, bar 2|b, when leaving its contact studs, cuts ofi the energizing circuit ofthe main contactor 8586, which is brought into the opening position. Owing to the inertia of motor l2, the roller 55 of switch 2| can just move past the inclined portion Y of cam 28, bar 2 la now establishing its contact and preparing the subsequent closing of the circuit of electro-magnet 68 (this position being that illustrated by Fig. 8).

After this, the releasing of the arm and the carriage of the drilling machine are obtained by depressing push button 8| and button 80, the circuit of which is now opened by bar 2|b is no with crank arm 32, has its notch 84' located opposite a roller 85 mounted on the end of a two position circuit-breaker bar 88, a spring 81 constantly applying the roller against the outline of cam 84. Bar 88 then closes the circuit of the signal lamp 80, which is thus: switched on, and

indicates that the locking operation is completed.

When the carriage and the arm are released, roller 85 is applied against the circular outline of cam 84, the circuit-breaker bar 88 then closthe carriage on slideways 2a, 2!) without producpractical and efficient embodiments of the present invention as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is: 1. A machine tool of the type described which comprises, in combination, a column, a radial arm carried by said column and pivotable about 'the axis thereof, two deformable jaws rigidly associated with said arm adapted to be applied on said column for locking said arm with respect to said column, a shaft mounted on said arm parallel thereto, two opposed crank pins carried by said shaft, connecting rods interposed between said crank pins and the ends of said Jaws respectively, whereby rotation of said shaft in one direction or the other moves said jaws toward, or away from, eachother and accordingly produces the locking of said arm on said column or its release, a crank arm journalled on said radial arm adapted to transmit rotary movement to said shaft, said crank arm being provided with a hole for ,tlre passage of said shaft coaxially therethrou'gl'r, a ring mounted in said hole between said crank arm and said shaft, coaxially with both and with substantial play with respect to both said crank arm. and said shaft, the inner face of said hole in the crank arm and the outer face of said ring being provided with corresponding grooves located in a given diametral plane, keys, slidable radially, engaged in said grooves for anguiarly interconnecting said crank arm and said ring, the inner face of said ring and the outer face of said shaft being provided with corresponding grooves located in a diametral plane at right angles to the first mentioned one, and keys, slidable radially, engaged in said last mentioned grooves for anguiarly interconnecting said ring and said shaft, whereby the reactions,

produced in said shaft by the coaction of the crank pins with the said Jaws, are substantially compensated by the said play between the crank arm and thelshaft and are not communicated to any material extent from said shaft to the crank arm and thence to the radial arm of the machine.

2. A machine tool of the type described which comprises, in combination, a column, a radial arm carried by said column and pivotable about the axis thereof, temporary means for locking said arm with respect to said column, said means being adapted to exert a temporary locking force upon said column, effective in a line passing through the axis thereof, final locking means operable while said temporary locking means are eifective, for fixing said arm with respect to said column, said final locking means being liable to cause pivotal movement of the radial arm aboutv said column, the'said temporary locking force being of sufficient magnitude to prevent pivotal movement of the radial arm about said column during the operation of said final locking means, and means for successively bringing into play said temporary locking means and said final locking means.

3. A'machine tool of the type described which comprises, in combination, a column, a radial arm carried by said column, a sleeve-rigid with said radial arm coaxially surrounding said column, whereby said radial arm is pivotable about the aids of said column, said sleeve being cut away so as to form a tongue deformable in the direction of the diametral plane of said column,

means for strongly applying said tongue against said column so as to lock said sleeve with respect to said column, said tongue and the means for applying it against said column forming temporary locking means developing a temporary locking force efiective in aline passing through the axis of said'column, final locking means'for fixing said arm with respect to said column, said final locking means being liable to cause pivotal movement-of said sleeve and radial arm about said column, the said temporary locking force being of sufiicient magnitude to prevent pivotal movement of the sleeve and radial arm about said column during the operation of saidfinal locking means, and means for successively bringi ing into play said temporary locking means and said final locking means.

4. A machine tool of the type described which comprises, in combination,-a column, a radial arm carried by said column, a sleeve rigid with said radial arm coaxially surrounding said 'column, whereby said radial arm is pivotable about the axis of said column, said sleeve being cut away so as to form a tongue deformable in the direction of the diametral plane of said column, electro-magnets carried by said tongue for strongly applying it against said column so as to lock said sleeve with respect to said column, said tongue and said electromagnets forming temporary locking means developing a temporary force locking effective in a line passing through the axis of; said column, final locking means for fixing said arm with respect to said column said final locking means being liable to cause pivotal movement of said sleeve and radial arm about said column,'i

the action of said electromagnets being sufiicient to prevent pivotal movement of the sleeve and radial arm about said column during the operation of said final locking means, and means for successively bringing into play said temporary locking means and saidfinal locking means.

5. A machine tool of the type described which comprises, in combination, a column, a radial arm carried by said column and pivotable about the axis thereof, temporary means for locking said arm with respect to said column, s'aid'means being adapted to produce a temporary locking force effective in a hne passing through the axis of said column, two deformable jaws rigidly associated with said arm adapted to be applied on said column for finally locking said arm with respect to said column, a shaft mounted on said arm parallel thereto, two opposed crank pins carried by said shaft, connecting rods interposed 'between said crank pins and the ends of said jaws,

. respectivel whereby rotation of saidshaft in one the axis thereof, temporary means for locking said arm with respect to said column, said means being adapted to produce a temporary locking force effective in a line passing through the axis of said column, final locking means for fixing said arm with respect to said column, said final locking means being liable to produce, when applied or released, tangential reactions of said column with respect to said arm, the temporary locking means being adequate to hold the arm against pivotal movement about the column in opposition to the said tangential reactions produced during the operation of the final locking means, and means for bringing into play said 'temporary locking means whenever said finallocking means are to be applied or released.

7. A machine tool of the type described which comprises, incombination, a column, a radial arm carried by said column and pivotable about the axis thereof, temporary electro-magnetic means for-locking said arm with respect to said column, said means being adapted to produce a temporary locking force efiective in a line passing through the axis of said column, final looking means for fixing said arm with respect toleased.

. means being liable to produce, when applied or direction or the other moves said jaws toward, or

' means for connecting said shaft with said arm comprising a bearing on said arm having a hole for receiving said shaft therewithin, the said hole released, tangential reactions of said column with respect to said arm,"a shaft for operating said a locking means, means for connecting said shaft with said arm comprising a bearing in which saidshaft extends, in a loose fit, permitting transverse movement of the shaft in said hearing substantially to the extent that such transyerse movement may be'induced in said shaft by said tangential reactions, a motor carried by said arm adapted to turn always in the same direction, means interposed between said motor' and said shaft for causing said shaft to oscillate' under the effect of the rotation of said motor,

' a cam driven by said motor, manual means for being of greater diameter than said shaft whereby to permit slight transverse displacement of said shaft with respect to said arm, and, hence,

to compensate for transverse displacement of said shaft caused by the coaction of the crank pins with the said jaws, such compensation reducing the reactions, of the final locking of the arm, which must be overcome by the temporary locking means.

6. A machine tool of the type described which comprises, in combination, a column,'a radial arm carried by said column and pivotable about closing the circuit of said motor, and means operative by said cam for automatically stopping said motor at the end of the application or release of said locking means.

9. A machine tool of the comprises, in combination, a column, a radial arm carried by said column and pivotable about the axis thereof, locking means for fixing said arm with respect to said column, said locking means being liable to produce, when applied or released, tangential reac ons of said column with t for operating said locking means, means forconnecting said shaft,

respecttosaidarm,as

with said am comprising a bearing in which said shaft extends, in a loose fit, permitting transverse movement of the shaft in said'b'earing substantially to the extent that such transverse type described which movement may be induced in said shaft by said a tangential reactions, a motor carried by said arm adapted to turn always in the same direction, means interposed between said motor and said shaft for causing said shaft to oscillate under the effect of the rotation of said motor, a cam driven by said motor, a contactor inserted in the feed circuit of said motor including an energizing circuit adapted, when closed, to close the circuit of said motor, a switch operative by said. cam, a circuit for maintaining the energizing of said contactor, two contacts in said switch, operative by said cam, both connected in shunt with said last mentioned circuit, said two contacts-being arranged successively to cut off and alternately to prepare the closing of, said circuit, whereby the device is re-set for a new operation at the end of each operation.

10. A machine tool .of the type described which comprises, in combination, a column, a radial arm carried by said column and pivotable about the axis thereof, locking means for fixing said tion, means interposed between said motor and said shaft for causing said shaft to oscillate under the effect of the rotation of said motor, a cam driven by said motor, a contactor inserted in the feed circuit of said motor including an energizing circuit adapted, when closed, to close the circuit of said motor, a circuit for maintaining the energizing of said, contactor, a switch operative by said cam, two contact elements in said switch, movable in response to the rotation of said cam, both connected in shunt with said last mentioned circuit, said two contact elements being arranged to produce the cutting oif, and alam with respect to said column, said locking temately to prepare the closing, of said last mentioned circuit, whereby the whole system is reset for a new operation at the end of each operation, the outline of the cam including two circular arcs of different respective radii, joined together by two portions oblique to the circumference of said cam, said switch including a roller rigidly connected to said contact elements and adapted to cooperate with the outline of said cam.

11. A machine tool of the type described which comprises, in combination, a column, a radial arm carried by said column and pivotable about the axis thereof, locking means for fixing said arm with respect to said column, said locking means being liable to produce, when applied or released, tangential reactions of said column with respect to said arm, a shaft for operating said locking means, means for connecting said shaft with said arm comprising a bearing in which said shaft extends, in a loose fit, permitting transverse movement of the shaft in said bearing substantially to the extent that such transverse movement may be induced in said shaft by said tangential reactions, a motor carried by said arm adapted to turn always in the same direction, means interposed between said .motor, and said the effect of the rotation of said motor, a cam driven by said motor, a contactor inserted in the feed circuit of said motor including an energizing circuit adapted, when closed, to close the circuit of said motor, a circuit for maintaining the energizing of said contactor, a switch including two contact elements both connected in shunt with said last mentioned circuit, said two elements being adapted to produce the cutting oil,

in shunt with the feed circuit of said motor between said contactor and said motor.

12. A machine tool of the type described which comprises, in combination, a column, a radial arm carried by said column and pivotable about the axis thereof, locking means for fixing said arm with respect to said column, said locking means being liable to produce, when applied or released, tangential reactions of said column with respect to said arm, a shaft for operating said locking means, means for connecting said shaft with said arm comprising a bearing in which said shaft extends, in a loose fit, permitting transverse movement of the shaft in said bearing substantially to the extent that such transverse movement may be induced in said shaft by said tangential reactions, a motor carried by said arm adapted to turn always in the same direction, means interposed between said motor and said shaft, for causing said shaft to oscillate under the eifect of the rotation of said motor, a cam driven by said motor, a contactor inserted in the feed circuit of said motor including an energizing circuit adapted, when closed, to close the circuit of said motor, a circuit for maintaining the energizing of said contactor, a switch including two contact elements both connected in shunt with said last mentioned'circuit, said two elements being adapted to produce the cutting off,

and alternately ,to prepare the closing. of said,

last mentioned circuit, and being both operatively connected with said cam, temporary means for locking said arm with respect to said column adapted to develop only forces passing through the axis of said column, said'temporary locking means including electro-magnets, means for electrically connecting said electro-magnets in shunt with the feed circuit of said motor between said contactor and said motor, and a delayed action electric transmission between said electro-magnets and said motor.

13, IA machine tool according to claim 11 which comprises a first push-button inserted in said energizing circuit, for producing the application of said locking means, and a second push button, also inserted in said energizing circuit, in shunt with the first, for producing the release of said locking means.

14. A machine tool according to claim 11 further including means, operative by the working of said locking means, for signalling the end of the operation ofsaid locking means.

15. A machine tool of the type described comprising a column, a radial tool supporting arm carried by said column andpivotable about the axis thereof, means for finally locking said arm against pivotal movement about said column,

shaft, for causing said shaft to oscillate under 1; and separate means for temporarily holding said arm in a desired position while said locking means'are being operated, the said holding means being adequate to hold said arm ,immovable against forces, induced by the action of said locklug-means, tending to cause said arm to shift froma desired position.

16. A machine tool according to claim 15, the

said holding means comprising portions of said column and of said arm, a holding device fixed a holding force upon the other of said portions effective in a line extending radially of said column, and means for establishing and disestablishing said force whereby, respectively, to hold said column and am against relative pivotal movement and to free said column andarm for such movement.

. upon one of said portions and adapted to exert .10

17. A machine tool according to claim 15, the

'said holding means comprising portions of said column and of said arm, a holding device fixed upon one of said portions and adapted to exert a holding force upon the other of said portions eflective in a line extending radially of said column, and means for establishing and disestab- 'lishing said force whereby, respectively, to hold MARCEL PEGARD. 

